mptcp: fix msk traversal in mptcp_nl_cmd_set_flags()

commit 8e9eacad7ec7a9cbf262649ebf1fa6e6f6cc7d82 upstream.

The MPTCP endpoint list is under RCU protection, guarded by the
pernet spinlock. mptcp_nl_cmd_set_flags() traverses the list
without acquiring the spin-lock nor under the RCU critical section.

This change addresses the issue performing the lookup and the endpoint
update under the pernet spinlock.

[The upstream commit had to handle a lookup_by_id variable that is only
 present in 5.17. This version of the patch removes that variable, so
 the __lookup_addr() function only handles the lookup as it is
 implemented in 5.15 and 5.16. It also removes one 'const' keyword to
 prevent a warning due to differing const-ness in the 5.17 version of
 addresses_equal().]

Fixes: 0f9f696a502e ("mptcp: add set_flags command in PM netlink")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index d96860053816adcdf1f7652a2760a7213cb35503..2137b7460deaa3dcdd883a73b4ca1b6ab5d31b31 100644 (file)
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -459,6 +459,18 @@ static unsigned int fill_remote_addresses_vec(struct mptcp_sock *msk, bool fullm
        return i;
 }
 
+static struct mptcp_pm_addr_entry *
+__lookup_addr(struct pm_nl_pernet *pernet, struct mptcp_addr_info *info)
+{
+       struct mptcp_pm_addr_entry *entry;
+
+       list_for_each_entry(entry, &pernet->local_addr_list, list) {
+               if (addresses_equal(&entry->addr, info, true))
+                       return entry;
+       }
+       return NULL;
+}
+
 static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 {
        struct sock *sk = (struct sock *)msk;
@@ -1725,17 +1737,21 @@ static int mptcp_nl_cmd_set_flags(struct sk_buff *skb, struct genl_info *info)
        if (addr.flags & MPTCP_PM_ADDR_FLAG_BACKUP)
                bkup = 1;
 
-       list_for_each_entry(entry, &pernet->local_addr_list, list) {
-               if (addresses_equal(&entry->addr, &addr.addr, true)) {
-                       mptcp_nl_addr_backup(net, &entry->addr, bkup);
-
-                       if (bkup)
-                               entry->flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
-                       else
-                               entry->flags &= ~MPTCP_PM_ADDR_FLAG_BACKUP;
-               }
+       spin_lock_bh(&pernet->lock);
+       entry = __lookup_addr(pernet, &addr.addr);
+       if (!entry) {
+               spin_unlock_bh(&pernet->lock);
+               return -EINVAL;
        }
 
+       if (bkup)
+               entry->flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
+       else
+               entry->flags &= ~MPTCP_PM_ADDR_FLAG_BACKUP;
+       addr = *entry;
+       spin_unlock_bh(&pernet->lock);
+
+       mptcp_nl_addr_backup(net, &addr.addr, bkup);
        return 0;
 }